I dropped mine the other day while a teeny bit intoxicated, onto a hard club floor, and it's held up fine. Had mine since very shortly after launch here in the UK, and mine has only a couple of tiny scuffs and scratches. And I'm not too kind to it either. Obviously the right fall will kill it, but that's the same with any phone. I've not used a case on any phone since I had an iPhone 3Gs years ago, and I've never felt that I've needed one since. I've killed an HTC Desire and a Sony Z1 in that time- the HTC was a screen onto a hard floor, and the the Z1 was crushed in a car door which wouldn't have been helped with a case. I've also had a Lumia 800 and 925 in that timeframe, which were equally misstreated but unaffected (the 925 had problems but not to do with being dropped!).
I'd certainly not worry about a Nokia device's sturdiness!